The Seattle Fault was first recognized as a significant seismic hazard in 1992, when a set of reports showed that about 1,100 years ago it was the scene of a major earthquake of about magnitude 7 – an event that entered Native American oral traditions.

First suspected from mapping of gravitational anomalies in 1965[1] and an uplifted marine terrace at Restoration Point (foreground in picture above), the Seattle Fault's existence and likely hazard were definitively established by a set of five reports published in Science in 1992.

These reports looked at the timing of abrupt uplift and subsidence around Restoration Point and Alki Point (distant right side of picture),[2] tsunami deposits on Puget Sound,[3] turbidity in lake paleosediments,[4] rock avalanches,[5] and multiple landslides around Lake Washington,[6] and determined that all these happened about 1,100 years ago (between 923 and 924 CE,[7] and most likely due to an earthquake of magnitude 7 or greater on the Seattle Fault.

Although the 923-924 CE earthquake was over a thousand years ago, local traditional stories have preserved an association of a powerful supernatural spirit – a'yahos, noted for shaking, rushes of water, and landsliding – with five locales along the trace of the Seattle Fault, including a "spirit boulder" called Psai-Yah-hus near the Fauntleroy ferry dock in West Seattle.

One model has the Seattle and Tacoma faults converging at depth to form a wedge, which is being popped up by approximately north–south oriented compression that ultimately derives from plate tectonics.

[21] A later model has part of the north-thrusting sheet forming a wedge between the sedimentary formations of the Seattle Basin and the underlying bedrock.

[23] This is about the time that the strike-slip movement on the north-striking Straight Creek Fault to the east ceased, due to the intrusions of plutons.

Others, such as the 2001 Nisqually earthquake, originate about 50 to 60 km (31 to 37 miles) below Puget Sound in the Benioff zone of the subducting Juan de Fuca plate; being so deep their energy is dissipated.

[37] There is also concern that a severe or prolonged event could cause failure of the Duwamish or Puyallup River deltas, where the main port facilities for Seattle and Tacoma are located (Harbor Island and Commencement Bay).